1. Field of the Invention
The invention relates to a method for the determination of the position of a reference point of a scanner relative to an incremental scale.
2. The Prior Art
Such a method serves, for example, the purpose of detecting in the controlling of automatic production machines the distance of travel between longitudinally displaceable objects. In such controls, the accuracy at which such distances of travel can be detected or acquired is of decisive importance for the manufacturing accuracy of the automatic machine.
Known methods make use of incremental scales with a mark resolution of up to about 2 um. So as to be able to exploit such predetermined resolution and, furthermore, to make an interpolation between the marks, the customarily used mark-reading scanners have to be guided with great precision. Hence for achieving a high measuring accuracy it is necessary to maintain very low manufacturing tolerances in the manufacture of such measuring systems, which is correspondingly reflected by the costs. Another drawback is that progressive wear of the guiding devices of the scanner constantly causes increasing measurement inaccuracies.